Oliver Archut custom made v78 pre for mastering - HPF switch not working?

[DaveP]

The fact that there is a 210K resistor in this position (not a preferred value) suggests it is part of a careful tuning/damping circuit. This could be for the IPT secondary. This is the most sensitive part of the amp so caution is advised, Oliver was not the sort of guy to do anything without a great deal of thought. (why use 210K when there are 200k or 220k resistors. Choose a cap with the best temperature stability, polyprop is a safe bet.
best
DaveP

 

[Darcy]

Thank you everyone for your replies. I will swap out the cap to ~6nf and report back.

dmp, interesting to hear that higher voltage rated caps have less distortion.

The switch itself works just fine, and there is a separate cap on the other side of the input transformer that I did not include in the schematic.

Bonnie1, thank you very much for your note. After some discussion, it seems the unit is working as intended, with a HPF frequency of 30 Hz, intended for mastering (Despite the panel saying 120 Hz). However since I use it as a preamplifier, I would like it to operate at a more useful frequency.

 

[Bonnie1]

Thank you everyone for your replies. I will swap out the cap to ~6nf and report back.

dmp, interesting to hear that higher voltage rated caps have less distortion.

The switch itself works just fine, and there is a separate cap on the other side of the input transformer that I did not include in the schematic.

Bonnie1, thank you very much for your note. After some discussion, it seems the unit is working as intended, with a HPF frequency of 30 Hz, intended for mastering (Despite the panel saying 120 Hz). However since I use it as a preamplifier, I would like it to operate at a more useful frequency.

Hello Darcy,
If you want to move the HPF up to 120hz, install .0047uf 400v film cap. If you have any further questions send an email. I'm not on the forums regular enough, current work load consumes most of our time.

-dennis M.

 

[Darcy]

Hello Darcy,
If you want to move the HPF up to 120hz, install .0047uf 400v film cap. If you have any further questions send an email. I'm not on the forums regular enough, current work load consumes most of our time.

-dennis M.

Understood thank you very much Dennis - I appreciate your specific instruction! I will email any further questions.

-d